This is a silly and absolutist position to take on HTTP. Everything depends on context, and in many cases it is far better to serve things over open HTTP than go offline.
If you had reason to previously set up your site with HTTPS, you should never fallback to serving anything other than static assets (and even then, you better have a damn good reason) over HTTP from that same domain. Period.
When you have publicly accessible resources that must be available to all, but you can't guarantee that the accessing systems are configured correctly to use HTTPS.
There are plenty of scenarios in which this happens online:
* Legacy systems (e.g. Aminet)
* Software distribution (e.g. apt mirrors)
* Anything involving FTP where a HTTP mirror would be useful (e.g. overcoming FW restrictions)
* Anything where permissionless access is a requirement (HTTPS is a permissioned system)
Sorry, but sometimes security is absolute.